Tank temp goes up at night...?

[Aquageorge]

Just a mystery. My tank temp goes up at night. Can't figure it out.

My chiller comes on at 80 degrees. Heater is on at 78 degrees (winter only).
All day, the chiller doesn't come on. At night, the chiller cycles the tank temp from 80 down to 79.5 several times.
The room has an air conditioner - always between 78 and 79 degrees.
During the day, the lights are on, at night they're off.
Circulation and sump pumps are about the same day and night, a little less flow at night.
UV light is on 24/7. A heat source, yes, but no difference between day and night.
At night, there is a small refugium grow light. (I turned it off for a couple of nights, no difference.)

My theories -
My condo building absorbs heat all day, then radiates heat into the interior at night.....
Something about CO2 (don't know what)...
No humans at night to walk around and create air circulation...(could maybe add a little nighttime circulation fan for the room, but the chiller is doing fine on it's own)

Anyway, no crisis, just a mystery.

 

[Peace River]

You mentioned the pumps are slower at night. Is it possible that there is less surface agitation at night and therefore less heat loss? Is it possible that the pumps are generating less heat at the lower speeds?

 

[vetteguy53081]

Less circulation and lower temps would likely trigger heater to go on

 

[Aquageorge]

Less circulation and lower temps would likely trigger heater to go on

Good idea. I checked the log, and the heater does not come on. The surface agitation idea could have some merit for sure. I'll increase the flow of the circ pumps at night and see.

 

[Peace River]

FWIW, the flow of the circulation pumps will tend to have more of an impact on heat based on the water surface agitation (not just flow in the tank).

 

[Aquageorge]

Ha! I discovered a nighttime heat source. My fishroom is in a walled-off portion of my garage. Our electrical panel is in there (probably not a heat source), but the Electric Car Charger is in there. The electric car charger comes on at NIGHT when rates are lower. That thing no doubt throws off some heat. Ha! (A little extra warming in the winter, anyway.)

 

[Peace River]

Good sleuthing!!! I'm glad you figured it out!